The present invention relates to a battery pack which includes a battery, and a battery protection circuit for protecting the battery from overcharge and overdischarge, and has a reduced number of inspection terminal for inspecting the operation of the battery protection circuit. The invention also relates to an inspection device for a battery pack for inspecting the operation of the battery protection circuit.
A battery pack using a rechargeable battery having a high energy density such as a lithium ion rechargeable battery is provided with a battery protection circuit for protecting the rechargeable battery from overcharge and overdischarge. FIG. 3 shows a constitution of a battery pack 20 provided with a battery protection circuit 21, and a device for inspecting the operation of the battery protection circuit 21.
As shown in FIG. 3, the battery pack 20 includes a rechargeable battery 28, and the battery protection circuit 21. A control circuit 29 constituting this battery protection circuit 21 monitors the voltage of the rechargeable battery 28. The circuit 29 controls to set a first FET 26 serially connected with an input/output circuit of the rechargeable battery 28 to a cutoff state when a voltage in an overcharged state is detected, and stops charging the rechargeable battery 28. The control circuit 29 controls to set a second FET 27 serially connected with the input/output circuit of the rechargeable battery 28 to a cutoff state when a voltage in an overdischarged state is detected, and stops discharging the rechargeable battery 28. This operation of the control circuit 29 protects the rechargeable battery 28 from overcharge and overdischarge.
The battery pack 20 is provided with inspection terminals 24 and 25 which are connected with the control circuit 29, and are used for inspecting the operation of the battery protection circuit 21 in addition to a positive electrode input/output terminal 22 and a negative electrode input/output terminal 23.
When an overcharge protection operation is inspected, a charging power supply 30 and an ammeter 31 are connected between the positive electrode input/output terminal 22 and the negative electrode input/output terminal 23, and a constant voltage power supply 32 is connected with the inspection terminals 24 and 25 as shown in FIG. 3. The charging power supply 30 supplies a charging power for setting the battery pack 20 to a charging state, and the constant voltage power supply 32 impresses an overcharge inspection voltage, which sets the rechargeable battery 28 to an overcharged state, between the inspection terminals 24 and 25. The control circuit 29 detects this overcharge inspection voltage, and controls the first FET 26 to cut off the input/output circuit, and the ammeter 31 detects the cutoff of the input/output circuit. Thus, it is determined whether the overcharge protection operation of the battery protection circuit 21 is normal or not based on whether the read of the ammeter 31 is zero or not when the overcharge inspection voltage is impressed by the constant voltage power supply 32.
When an overdischarge protection operation is inspected, a discharging load 33 and the ammeter 31 are connected between the positive electrode input/output terminal 22 and the negative electrode input/output terminal 23, and the constant voltage power supply 32 is connected with the inspection terminals 24 and 25. Connecting the discharging load 33 sets the battery pack 20 to a discharging state, and the constant voltage power supply 32 impresses an overdischarge inspection voltage, which sets the rechargeable battery 28 to an overdischarged state, between the inspection terminals 24 and 25. The control circuit 29 detects this overdischarge inspection voltage, and controls the second FET 27 to cut off the input/output circuit, and the ammeter 31 detects the cutoff of the input/output circuit. Thus, it is determined whether the overdischarge protection operation of the battery protection circuit 21 is normal or not based on whether the read of the ammeter 31 is zero or not when the overdischarge inspection voltage is impressed by the constant voltage power supply 32.
However, since the battery pack 20 having the conventional constitution requires the two inspection terminals 24 and 25 for inspecting the battery protection circuit 21, there is such a problem as the area of a circuit board and the volume of a pack case increase. As the size and the thickness of portable devices on which the battery pack 20 is mounted reduce, reducing the size and the thickness of the battery pack 20 becomes necessary, and reducing the space for providing the inspection terminals 24 and 25 becomes desired.
Since wiring connected with the individual inspection terminals 24 and 25 may receive electromagnetic radiation from outside, or may generate unnecessary electromagnetic radiation to outside, the wiring may influence a device on which the battery pack 20 is mounted, or may cause a malfunction of the battery protection circuit 21.
An object of the present invention is to provide a battery pack using one inspection terminal to inspect the operation of the battery protection circuit, and an inspection device for the inspection.
A first aspect of the present invention is a battery pack which includes a rechargeable battery, a positive electrode input/output terminal connected with a positive electrode of the rechargeable battery, a negative electrode input/output terminal connected with a negative electrode of the battery, switching elements serially connected with an input/output circuit extending from the rechargeable battery to the positive electrode input/output terminal and the negative electrode input/output terminal, and a control circuit for monitoring a voltage between the positive and negative electrodes of the rechargeable battery, and setting the switching element to a cutoff state when an overcharge voltage in an overcharged state, or an overdischarge voltage in an overdischarged state is detected. The battery pack further includes an inspection terminal for outward extending a positive electrode voltage input terminal of the control circuit used for receiving the positive electrode voltage of the rechargeable battery, and a part between the inspection terminal and the negative electrode input/output terminal is constituted as an input unit for an inspection voltage for inspecting an overcharge protection operation and an overdischarge protection operation by the control circuit.
A second aspect of the invention is an inspection device for a battery pack which includes a rechargeable battery, a positive electrode input/output terminal connected with a positive electrode of the rechargeable battery, a negative electrode input/output terminal connected with a negative electrode of the battery, switching elements serially connected with an input/output circuit extending from the rechargeable battery to the positive electrode input/output terminal and the negative electrode input/output terminal, a control circuit for monitoring a voltage between the positive and negative electrodes of the rechargeable battery, and setting the switching element to a cutoff state when an overcharge voltage in an overcharged state, or an overdischarge voltage in an overdischarged state is detected, and an inspection terminal for outward extending a positive electrode voltage input terminal of the control circuit used for receiving the positive electrode voltage of the rechargeable battery. The inspection device detects an overcharge protection operation or an overdischarge protection operation of the battery pack by current detection means installed in a charging circuit or a discharging circuit while a charging power supply or a discharging load is connected between the positive electrode input/output terminal and the negative electrode input/output terminal of this battery pack, and an inspection voltage corresponding to the overcharge voltage or the overdischarge voltage is impressed on the control circuit. The inspection device is provided with inspection voltage generation means for generating the inspection voltage from a voltage between the positive electrode input/output terminal and the negative electrode input/output terminal, and impressing the inspection voltage between the inspection terminal and the negative electrode input/output terminal.
A third aspect of the invention is an inspection device for a battery pack which includes a rechargeable battery, a positive electrode input/output terminal connected with a positive electrode of the rechargeable battery, a negative electrode input/output terminal connected with a negative electrode of the battery, switching elements serially connected with an input/output circuit extending from the rechargeable battery to the positive electrode input/output terminal and the negative electrode input/output terminal, a control circuit for monitoring a voltage between the positive and negative electrodes of the rechargeable battery, and setting the switching element to a cutoff state when an overcharge voltage in an overcharged state, or an overdischarge voltage in an overdischarged state is detected, and an inspection terminal for outward extending a positive electrode voltage input terminal of the control circuit used for receiving the positive electrode voltage of the rechargeable battery. The inspection device detects an overcharge protection operation or an overdischarge protection operation of the battery pack by current detection means installed in a charging circuit or a discharging circuit while a charging power supply or a discharging load is connected between the positive electrode input/output terminal and the negative electrode input/output terminal of this battery pack, and an inspection voltage corresponding to the overcharge voltage or the overdischarge voltage is impressed on the control circuit. The inspection device is provided with a voltage memory circuit for storing the battery voltage of the rechargeable battery, a DC voltage power supply for generating voltages for inspecting the overcharge protection operation and the overdischarge protection operation, and a inspection voltage generation circuit for generating the inspection voltage from a voltage difference between an output voltage of the voltage memory circuit, and an output voltage of the DC voltage power supply, and a voltage between the positive electrode input/output terminal and the negative electrode input/output terminal, and impressing the inspection voltage between the inspection terminal and the negative electrode input/output terminal.
A fourth aspect of the invention is an inspection device for a battery pack which includes a rechargeable battery, a positive electrode input/output terminal connected with a positive electrode of the rechargeable battery, a negative electrode input/output terminal connected with a negative electrode of the battery, switching elements serially connected with an input/output circuit extending from the rechargeable battery to the positive electrode input/output terminal and the negative electrode input/output terminal, a control circuit for monitoring a voltage between the positive and negative electrodes of the rechargeable battery, and setting the switching element to a cutoff state when an overcharge voltage in an overcharged state is detected, and an inspection terminal for outward extending a positive electrode voltage input/output terminal of the control circuit used for receiving the positive electrode voltage of the rechargeable battery. The inspection device detects an overcharge protection operation of the battery pack by current detection means installed in a charging circuit while a charging power supply is connected between the positive electrode input/output terminal and the negative electrode input/output terminal of this battery pack, and an inspection voltage corresponding to the overcharge voltage is impressed on the control circuit. The charging power supply supplies a charging power having a voltage corresponding to the overcharge voltage, and the output voltage of the charging power supply is impressed between the inspection terminal and the negative electrode input/output terminal in a charging state where charging voltage generation means drops the output voltage from the charging power supply to a normal charging voltage, and the charging voltage is impressed between the positive electrode input/output terminal and the negative electrode input/output terminal.
With the above constitutions, since the negative electrode input/output terminal is shared by a negative electrode terminal on which the inspection voltage is impressed, and only the positive electrode inspection terminal is necessary, the conventional multiple inspection terminals are reduced to one location, the size of the circuit board is reduced. Further, since the number of wiring lines connected with the terminals is reduced, the electromagnetic radiation from the wiring and the influence of the external electromagnetic radiation on the device are reduced.